"It's only when molybdenum becomes highly oxidized that it is able to influence how early life formed," and this type of the chemical element "could only have been available on the surface of Mars and not on Earth…because three billion years ago the surface of the Earth had very little oxygen," Benner told a gathering of geochemists at this year's Goldschmidt Conference in Florence, Italy.

Benner supports the idea that life arrived on Earth via "a Martian meteorite, rather than starting on this planet."

Here he explains why he thinks molybdenum is so important to to the origin of life:

"Certain elements seem able to control the propensity of organic materials to turn into tar, particularly boron and molybdenum, so we believe that minerals containing both were fundamental to life first starting."

"Analysis of a Martian meteorite recently showed that there was boron on Mars; we now believe that the oxidized form of molybdenum was there too."

Benner says "the evidence is building that we are actually Martians," but expresses gratitude that the trip to the Blue Planet was eventually made:

"It's lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life. If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell."